1. Field of Invention
The present invention relates to a resonator piece comprising, for example, crystal, a resonator including the resonator piece, an oscillator disposed with the resonator, and an electronic device.
2. Description of Related Art
Conventionally, a crystal tuning fork resonator piece, which is, for example, a resonator piece, is configured as shown, for example, in FIG. 9. The crystal tuning fork resonator piece 10 includes a base portion 11 and two arm portions 12 and 13 that are formed so as to project from the base portion 11. Additionally, grooves 12a and 13a are disposed in the two arm portions 12 and 13. The grooves 12a and 13a are similarly disposed on back surfaces of the arm portions 12 and 13 that are not shown in FIG. 9.
For this reason, as shown in FIG. 10, which is a cross-sectional view along E–E′ of FIG. 9, the arm portions 12 and 13 are formed so that the cross-sectional shapes thereof have substantial “H” shapes. The substantially H-shaped crystal tuning fork resonator piece 10 has the characteristic that, even if the size of the resonator piece is made significantly compact than the conventional piece, resonation loss of the arm portions 12 and 13 is kept low and the CI value (crystal impedance or equivalent series resistance) can also be kept low.
For this reason, the substantially H-shaped crystal tuning fork resonator piece 10 is particularly suited, for example, for a resonator of which compactness and high-precision performance are demanded. As this resonator, there is a compact resonator or the like whose resonance frequency is, for example, 32.768 kH, and using the substantially H-shaped crystal tuning fork resonator piece 10 as a resonator piece in this resonator is being investigated. Additionally, a compact resonator or the like whose resonance frequency is 32.768 kH will eventually be incorporated and used in precision equipment, such as watches and the like.
When a current is applied from the outside to the above mentioned substantially H-shaped crystal tuning fork resonator piece 10, the arm portions 12 and 13 resonate. Specifically, groove electrodes are formed in the grooves 12a and 13a shown in FIGS. 9 and 10, and side surface electrodes are formed in both side surfaces 12b and 13b, which are surfaces of the arm portions 12 and 13 in which the grooves 12a and 13a are not disposed. Additionally, when the current is applied, an electrical field arises between the groove electrodes and the side surface electrodes, so that the arm portions 12 and 13 resonate.
As described above, the current is applied to the groove electrodes and the side surface electrodes from the outside. Specifically, the current is supplied from the outside to the groove electrodes and the side surface electrodes via a base portion electrode disposed at the base portion 11 of the crystal tuning fork resonator piece 10.
For this reason, connection electrodes that connect the base portion electrode with the groove electrodes and the side surface electrodes become necessary. Of these connection electrodes, a groove electrode-use connection electrode that connects the base portion electrode with the groove electrodes is disposed at a base portion surface 11c in FIG. 9. Also, side surface electrode-use connection electrodes that connect the base portion electrode and the side surface electrodes are disposed, for example, at the base portion surface 1lc and an arm portion surface 12c. 
However, because the groove 12a and the groove electrode are formed in the arm portion surface 12c, the side surface electrode-use connection electrode disposed at the arm portion surface 12c must be disposed in a portion where the groove 12a is not formed (diagonal line portion in FIG. 9), therefore, the side surface electrode-use connection electrode is disposed in this region.